Outflow-subtracted spectra of CO 1−0, CO 2−1, CO 9−8, ¹³CO 1−0, ¹³CO 10−9, C¹⁸O 1−0, and C¹⁸O 9−8 (black) as observed toward IRS 1, overplotted with the synthetic emission as calculated with RATRAN, after having applied the lower density east hemisphere from DUSTY models (red) and the high density west hemisphere (blue). We observe no significant differences between the two cases with the exception of the low-J transitions of the isotopologues. While the model fits the observations for the lower transition lines well, it fails to reproduce the observed higher transition lines.